Viscosimeter

ABSTRACT

An apparatus for measuring the viscosity of a liquid product in a vessel, for instance, a reaction vessel, a dilution vessel or an evaporator, includes a measuring cell whose measuring chamber is connected to a capillary through which the liquid may be emptied from or filled into the chamber, the time of starting and ending the emptying or filling being accompanied by electric control pulses so that this time interval may be measured and the flow of a gas supplied to the cell under pressure is reversed.

1451 Aug. 1,1972

United States Patent Geerdes et al.

[54] VISCOSIMETER FOREIGN PATENTS OR APPLICATIONS 1,566,139 3/1969France.............................

[72] Inventors: Dirk J. Geerdes, Woensdrecht; Cor- .73/56 nelis J. n Vm, Bergen P 121,595 10/1958 U.S.S.R. Zoom, both of Netherlands [73]Assignee: Kunstharsfabriek Synthese N.V.,

Primary Examiner-Louis R. Prince Assistant Examiner-Joseph W. RoskosAttorneyl(urt Kelman [22] Filed:

ABSTRACT An apparatus for measuring the viscosity of a liquid [52] U 8Cl 73/56 product in a vessel, for instance, a reaction vessel, a [51]lnzcl dilution vessel or an evaporator, includes a measuring [58] Field73/56 55 cell whose measuring chamber is connected to a capillarythrough which the liquid may be emptied from or References Cited filledinto the chamber, the time of starting and ending UNlTED STATES PATENTS3,071,961 1/1963 Heigl et the emptying or filling being accompanied byelectric control pulses so that this time interval may be measured andthe flow of a gas supplied to the cell under pressure is reversed.

73/55 3,242,720 3/1966 Zavasmk .............73/56 3,540,264 11/1970Cerrutti l3 Clains, l1 DrawingFigures TCHES 8 TIME RELAYS l l l l swlPNENTED E 1 I97? 3. 680.362

sum 3 0F 8 INVENTORS. DIRK J. 'GEERDES CORNELIS J. VAN VESSEM mud: 7.

AGENT PATENTEmm; H972 3.680.362

' sumuora l N VEN TORS.

- DIRK J. GEERDES CORNELIS J. VAN VESSEM AGENT FAT LINSEED OIL'ALKYDRESIN O O I A VISCOSITY IN DP AT 0 OFA 50% SOLUTION FLOW TIME IN SEC. AT200C 5 FAT SOYA-ALKYD RESIN l-I 8 IIO- FIG.?

FLOW TIME IN SEC.

7'0 8'0 9'0 I00 Iio I20 I'30 I40 VISCOSITY IN DP AT 20C OFA SOLUTIONINVENTORS. DIRK J. GEERDES CORNELIS J. VAN VESSEM Kw ii 74 AGENTPATENTED 1 I973 A 3.680.362

' sum 7m 8 MEDAIUM FAT LINSEED OlL-A'LKYD RESIN FLOW TIME IN SEC. AT 200C.

zo zol sbol 340! 240 280 320 3 0 VISCOSITY m DP AT 2oc OF A 50% SOLUTIONMEDIUM FAT SOYA-ALKYD RESIN 240- I FLOW TIME IN SEC. AT 200 1 I T I Q II l I020 304050607080 VISCOSITY IN DP AT 20'C OF A 50%SOLUTION IN XYLENEINVENTORS.

DIRK J. GEERDES CORNELIS J. VAN VESSEM BY Z AGENT PNENTEDMJ I I972 SHEET8 [IF 8 LITTLE FAT ALK-YD RESIN ONA BASIS OF SATURATED FATTY ACIDS FIGJOVISCOSITY IN DP AT 20 C OF A 60% SOLUTION IN XYLENE LITTLE FATCOCO-ALKYD RESIN FIG.I I

' VISCOSITY IN DP'AT 20C OF A 50% SOLUTION KM; K

- AGENT VISCOSIMETER The invention relates to an apparatus for measuringthe viscosity in vessels by means of a capillary viscosimeter during thepreparation of intermediate products and final products.

Measuring the viscosity is in many chemical and physical processes anact of great importance in order to have the process controlledcorrectly. An examplehereof is the preparation of synthetic resins, inwhich the viscosity as a rule increases during the polymerization and/orcondensation process. A final product of a certain resin type must showa viscosity within a determined range, mostly indicated for a certainconcentration in an appropriate solvent to obtain the desiredproperties. It is clear that for the course of the reaction as well asfor the determination of the end of the reaction, a quick and frequentmeasuring of the viscosity is of great importance.

So far the measuring of the viscosity during the preparation ofsynthetic resins has been carried out mostly outside the reactor. As arule, samples are taken from the reaction vessel during the process atcertain intervals of time, which samples are dissolved in a solvent,such as white spirit or xylol, to a certain concentration. The viscosityof the resin solutions obtained can then be measured in various manners,such as by measuring the fiow time in seconds at C of the resin solutionfrom a measuring cup, the comparative determination of the viscosity ofa resin solution with the Gardner-Bubble viscosimeter or by means of thefalling ball method according to Hoppler. All these and similar methods,by which the viscosity of the resin solution is measured at lowtemperature, as a rule 20 or C, are, however, if carried out exactly,cumbersome and time-consuming. The result is known only after a periodof time of 20-30 minutes after having taken a sample from the reactionvessel. The determination of the correct moment at which the reactionmust be stopped is for that reason often inexact. All this has asconsequence that the reproducibility of the viscosity of the finalproduct often leaves much to be desired.

It is the primary object of the present invention to overcome these andother disadvantages and to make it possible to make rapid and successivemeasurements of the melt viscosity of a liquid reaction product, forinstance during a polymerization or condensation process, and thus toobtain a very good reproducibility of the final viscosity of eachproduct.

The measurement of the viscosity by the apparatus of this invention isbased on the known I-Iagen-Poiseuille principle that the time requiredto have a constant volume of a liquid flow through a capillary isdirectly proportional to the viscosity and the length of the capillary,and inversely proportional to the pressure dif ing the reaction bysimply measuring the time necessary for pressing a constant volume ofthe liquid through a capillary at an adjusted pressure difference.

The above and other objects, advantages and features of the presentinvention will be better understood by reference to the followingdetailed description of certain preferred embodiments thereof, taken inconjunction with the accompanying drawing wherein FIG. 1 is a schematicview of one embodiment of an apparatus according to thisinvention;

FIG. 2 is a similar view of a modification of this apparatus;

FIG. 3 shows still another embodiment;

FIG. 4 shows a modification of this embodiment,

FIG. 5 is a graph illustrating the results of a series of tests; and

FIG. 6 to 11 are graphs illustrating the relationship of the meltviscosity and solution viscosity of certain test resins.

Referring now to the drawing and first to FIG. 1, the apparatus 'isshown to comprise a measuring cell I mounted in, and surrounded by, animmersion tube 2, both of which are immersed in the liquid in reactionvessel 3. The tube 2 has a plurality of vertically spaced ports 4 sothat a certain amount of the liquid may flow through the tube, whichserves to prevent excessive turbulences that may be caused by a stirrerin the reaction vessel in the vicinity of capillary 6. i

The measuring cell defines a measuring chamber 5 having a pre-determinedvolume, for instance cc, the upper end of the measuring chamber beingdelimited by the end of conduit 7 and the lower end of the measuringchamber leading into a capillary tube '6. A flow of an inert gas, suchas nitrogen, enters the mea suring cell under a predetermined pressurethrough valve 16. While the cell is filled with liquid from the reactionvessel to measure its viscosity, the valve 23 has been adjusted tosupply a small gas flow of about five to 10 liters per hour throughconduit 8 into cell 1, the gas flowing through rotameter 17, where itsflow is measured, and escaping again through conduit 7, the valveposition 2 of the solenoid valve 9 being open to vent the gas to thesurrounding atmosphere. After the measuring chamber 5 has been filled sothat the liquid blocks the output end of conduit 7, the flow of gas ofabout 50 to 100 liters per hour supplied by valve 22 passes throughconduit 7 into cell 1 and presses the liquid out of the measuringchamber 5 and through capillary 6, solenoid valve 9 being repositionedin a manner to be described hereinafter.

A compensation tube 10 is also mounted in the measuring cell 1 tocompensate for variations in the pressure and liquid level in reactionvessel 3, in a manner to be also described hereinafter.

The viscosity measuring apparatus may be used under different pressureconditions, for which purpose the outlet 0 of valve'l4, the outlet 2 ofvalve 9 and the outlet 15 of vessel 11 may be connected to the spaceabove the liquid level in reaction vessel 3. The measuring result, i.e.the time required to press the liquid out of the measuring chamber ofcell 1, is independent on the immersion depth of the cell in the liquidand the pressure over the surface of the liquid in the reaction vessel.

The apparatus operates in the following manner:

When the apparatus is out of operation, gates l() of solenoid valve 14and gates l of solenoid valve 9 are in communication. Thus, any gassupplied escapes through the open gates of valve 14 and through thecapillary 6 into the liquid in the reaction vessel.

When the apparatus is switched on, gates 1 and 2 of valve 9 are broughtinto communication and a time relay connected to valve 9 is actuated.The time relay is adjustable to determine the very short delay in whichthe solenoid valve 14, which is also connected to the relay, is switchedover from position 1-0 to the position wherein the gates 1 and 2 are incommunication. In this short time lag between the operation of valves 9and 14, the gas pressure in conduits 7,8 and in measuring cell 1 isdischarged through open gate 2 of valve 9. Now, the measuring cell 1 isfilled with the liquid from the reaction vessel whose viscosity is to bemeasured.

While the measuring chamber 5 fills up, the inert gas flows throughvalve 23, rotameter .17 and communicating gates l and 2 of valve 14 intoconduit 8 whence it is discharged into the measuring cell and escapestherefrom through conduit 7 and the communicating gates 1 and 2 of valve9. This continues as long as the liquid in the measuring chamber doesnot block access to conduit 7.

Meanwhile, a flow of about 50 to 100 liters per hour of inert gas passesthrough adjustable valve 22 and rotameter 19 into tube l8 which isadjustably positioned in vessel 13, whence the gas flows out throughconduit 12 into compensation tube which vents the gas into the liquid inreaction vessel 3. Since, during the filling period of the measuringcell, the gates 1 and 2 of valve 9 are in communication while the valvegate 0 is blocked, no gas will pass through the valve 9 from conduitwhich branches off tube 18.

The vessel 13 is closed on'top, the vessel being partially filled withan electrically conductive liquid, for instance a 1 percent KOH solutionin a mixture of water and glycol, and the pressure p in the vessel abovethe liquid level beingequal to the sum of the hydrostatic pressure ofcolumn h extending from the outlet ends of the compensation tube 10 andcapillary 6 to the surface of the liquid in'the reaction vessel, and thepressure over the liquid level in the reaction vessel. During filling,the pressure in conduit 20 is, therefore, equal to the sum of p and thehydrostatic pressure p of column k extending from the outlet end of tube18 to the surface of the conductive liquid in vessel 13.

A pair of electrodes k and k, are positioned in vessel 13, withelectrode k extending into tube 18 to a point about an inch or so fromthe lower or outlet end of the tube. During filling of the measuringchamber 5 with liquid and while inert gas is supplied to conduit 18 andqbubbled therefrom into the electrically conductive liquid in vessel 13,the conductive connection between electrodes k and k is interrupted. Assoon as the measuring chamber has been filled and the'lower end ofconduit 7 has been blocked by the liquid, the inert gas flowing into themeasuring chamber through conduit 8 can no longer escape through conduit7. This causes a small over-pressure to develop in conduit 8 and to backup into branch conduit 21 leading from conduit 8 into vessel 11. Vessel11 is also partially filled with an electrically conductive liquid, forinstance the same as that in vessel 13, a pair of electrodes k and kbeing positioned in vessel 11, with the electrode k; being mounted intube 21. When the overpressure in conduit 21 depresses the level of theelectrically conductive liquid therein, the electrical connectionbetween electrodes k, and k is interrupted as soon as the liquid levelis below electrode k Electrodes k -k and k -k are connected to anamplifier which supplies the electrodes with a voltage, for instance analternating voltage of a maximum of one volt. These electrodes produceelectrical control signals for operating the solenoid valves, the timerelay,

the switches and the time indicator dial or recorder in the followingmanner:

When measuring chamber 5 has been filled with the liquid whose viscosityis to be measured, access to conduit 7 is thus blocked by the liquid, aslight overpressure develops in conduit 8 and conduit 21, the level ofthe electrically conductive liquid in vessel 11 is tion wherein gates 0and l of valve 9 are in communica-' tion so that gas from conduit 20 mayenter into conduit 7. In other words, the gas flow through the measuringcell is reversed, and the gas flowing from conduit 7 begins to press theliquid out of the measuring chamber 5 into capillary 6.

Simultaneously, the time recorder is switched on to register the timerequired to press the liquid out of measuring chamber 5. Alsosimultaneously, an adjustable time relay interrupts the electricalcontact between electrodes k and k, for a few seconds. This is toprevent the two electrodes from coming into electrical contact due tothe fact that the electrically conductive liquid in vessel 13 rises intube 18 to the level of electrode k by the sudden temporary pressuredrop in conduit 20 when the valve 9 is opened to communicate withconduit 20. At this point, the measuring cell is emptied under a gaspressure p,+p through capillary 6. During this period, too, the gaspressure flowing in through valve 22 and rotameter 19 at an hourly rateof about to 100 liters escapes through conduit 18, vessel 13, conduit 12and compensation tube 10 into the reaction vessel 3. Consequently, anypressure variations occurring in the reaction vessel are compensatedduring measuring.

At the moment the measuring cell 1 is emptied, the

' gas pressure in conduit 7 drops from p +p to p,, which In thisapparatus, however, switch means k k and vessel 11 have been replaced bya pressure differential sensitive switch 24 and the switch means k -kand the vessel 13 have been replaced by the combination of a pressuredifferential sensitive switch 25 and the pressure balanced reducingvalve 26. Switch 25 and the pressure balanced reducing valve 26 functionequivalently to electrodes k k in vessel 13. The pressure balancedreducing valve 26 delivers a gas pressure p +p in conduit 20 when thegas pressure in conduit 12 At the moment the pressure in conduit 20drops from p +p to 1,, due to the fact that the measuring chamber isempty, the valve 26 is not able to produce the additional pressure pbecause the gas escapes through the capillary 6. As a consequencethereof, the pressure differential switch 25, connected to solenoidvalves 14 and 9 switches valve 14 from the position wherein gates 1 and0 are in communication to the position wherein gates 1 and 2 are incommunication, and switches valve 9 from the position wherein gates 0and I are in communication to the position wherein gates l and 2 are incommunication. As a consequence thereof, valve 26 increases again thepressure in conduit 20 from p to p P2- The pressure differentialsensitive switches 24 and 25 and the pressure balanced reducing valve 26are commercially available pneumatic instruments.

In a variant of the embodiment of FIG. 2 (not illustrated) the pressurebalanced reducing valve 26 has been eliminated and its function is takenover by the compensation tube by extending this tube sufficiently toincrease the hydrostatic pressure in this tube by an amount equal tothat of column h in FIG. 1.

In this embodiment the conduits and 12 are interconnected so that,during the period of time when the liquid whose viscosity is measured ispressed out of the measuring chamber, the pressure in conduits 20 and 12is the same, i.e. p +p At the moment the gas can escape throughcapillary 6, because the measuring chamber is empty, the pressure inconduit 20 drops to P1, as a consequence of which switch actuates thecontrol circuit to advance to the next cycle.

In the embodiment as shown in FIG. 3 the switching means for the controlcircuit has been replaced by two conductivity measuring devices 24a and25a positioned in the measuring cell, these devices producing electricalcontrol pulses in response to changes in conductivity from zero to ameasurable value. The inert gas is supplied under a predeterminedpressure by metering valve 16, and when the apparatus is out ofoperation, gates 0 and 1 of solenoid valve 14 are open so that the gasescapes through capillary 6 into the liquid in the reaction vessel. Whenthe apparatus is switched on, gates l and 2 of valve 14 are brought intocommunication, as a consequence of which the measuring cell is filledunder the influence of the hydrostatic pressure difference between theoutlets of the capillary 6 and the conduit 10a. When the liquid reachesthe conductivity measuring device 24a, the device produces an electricalcontrol pulse which starts the time recorder. When the liquid level inmeasuring cell la reaches the conductive measuring device 25a, thedevice produces an electrical control pulse stopping the time recorderand actuating valve 14 by bringing gates l and 0 into communication, asa consequence of which the cell is emptied under the influence of thegas pressure. As soon as the liquid level has passed the conductivitymeasuring device 24a, valve 14 is actuated so that gates 1 and 2 arebrought into communication again. At that moment a new measuring cyclestarts.

FIG. 4 shows another modification of the apparatus. Also here theelectrical pulses are produced by change of conductivity from zero to ameasurable value and vice versa. The insert gas is supplied under apredetermined pressure by a reducing valve 16. When the apparatus is outof operation, gates l and 2 of the solenoid valve 14 are open so thatthe gas escapes through capillary 6 into the liquid in the reactionvessel. When the apparatus is switched on, gates 0 and l are broughtinto communication, as a consequence of which the measuring cell isfilled. When the liquid reaches the conductivity measuring device 25a,the device produces an electrical pulse which actuates valve 14, as aconsequence of which gates l and 2 are brought into communication andthe time recorder is started. Thereupon the gas pressure in themeasuring cell, which is in communication with the compensation tubepresses the liquid in the measuring cell through the capillary. When theliquid level in the measuring cell la reaches the conductivity measuringdevice 24a the device produces again an electrical pulse delay stoppingthe time recorder and actuating an adjustable time relay to start themeasuring cycle again.

Also in this embodiment the conductivity measuring devices 24a and 25amay be replaced by capacity measuring devices operating in an equivalentmanner.

It is obvious from the above description that the capillary viscosimeterhereinabove described is arranged for use in vessels for chemical andphysical processes and makes, moreover, measurements in series possible.By measuring the time necessary for pressing a constant volume ofliquid, determined by the dimensions of the measuring chamber, through acapillary at an adjusted pressure difference, the melt viscosity of asynthetic resin, for instance, may be determined in seconds and at atemperature prevailing in the reaction vessel. As will be understood,the melt viscosity is the viscosity of the liquid reaction product atthe elevated temperature prevailing during the polymerization orcondensation reaction.

By calibrating the capillary viscosimeter at various temperatures withliquids of known viscosity, it is also possible to express the viscosityin poises. In this connection, however, it is as a rule less importantfor the control of a process to know an absolute viscosity than a quickand accurate comparative information, e.g. to be obtained by timemeasurement, the more so as one measurement of the dynamic or kinematicviscosity of non-Newton liquids cannot be considered adequate for thedefinition of the complete flow character.

A condition for the practical use of the apparatus in the preparation ofsynthetic resins, where the melt viscosity instead of the viscosity ofthe solution is measured, is the presence of a close relationshipbetween the two forms. As already stated, the final product must show asa rule a viscosity range which is mostly indicated as the viscosity of asolution of the product at low temperature. It has been found that, ofeach tested resin type, the melt viscosity isdecisive for the viscosityof the solution, as elucidated by the tests described below.

During the preparations of a number of alkyd resins.

and polyesters, differing in composition and conden'sation temperature,resin samples were taken from the reaction vessel. These resin samplesof increasing viscosity were diluted in a solvent to a predeterminedConcentration. The viscosity of the-resulting resin solutions wasdetermined by means of a so-called bubble viscosimeter according to theprinciple of Gardner- Holdt at 20 C by comparison. At the time of takingthe samples, the melt viscosity of the resin inthe reservoir wasdetermined with the capillary viscosimeter according to the inventionand expressed in seconds of flow time. The results of the alkyd resinsand polyester resin and phenolic resin modified rosin ester mentioned intable I are stated in FIG. 5.

i TABLE 1 Resin Type of Conden- Solvent concent- -No. resin sation usedfor ration of temp. solution resin in viscosity solvent 1 medium linseedoilwhite alkyd resin 230C .spirit 50% 2 medium soyabean oilwhite alkydresin 230C spirit 50% 3 short oil alkyd resin 230C xylol 50% 4 long oilsoya white alkyd resin 240C spirit 50% 5 long oil alkyd resin based onsun-flower white fatty acids 240C spirit 50% 6 short oil resin based onsaturated fatty acids 225C xylol 60% 7 polyester 210C Xylol butanol 50%8 phenolic resin modified resin ester 270C 55% toluol The almoststraight course of the curves shows clearly that there is closerelationship between the melt viscosity and solution viscosity duringthe condensation tionship between the last-determined melt viscosity andthe viscosity of the solution of one and the same resin type. FIGS.6,7,8 and 9 also show the good reproducibility; an almost equal meltviscosity of the final products of one and the same resin type givespractiplied to the preparation of other products, such as phenolicresins, amino resins, vinyl resins, polyesters, polyurethane resins,acrylate resins, etc.

. In general the invention, in addition to the examples alreadymentioned, can be used wherever it is of importance to measure theviscosity during the preparation of intermediate products and finalproducts I directly in a reaction vessel, dilution vessel or evaporator.

Some important conditions for accurate and reproducible measurements ofthe viscosity in reaction vessels by means of so-called capillaryviscosimeters include, first a careful control of the temperature of theliquid in the reaction vessel, the influence of the temperature of theliquid to be measured upon the melt viscosity being considerable,whereforethe deviation may maximally amount to i 15 C; in the secondplace, the the amount of liquid in the measuring cell to be measuredmust be constant for each measuring; in the third place, the pressuredifference under which the measuring cell is emptied or filled must be,the same at each measuring; the hydrostatic pressure of the liquidcolumn calculated from the bottom of the capillary up to the liquidsurface and the pressure over the liquid surface in the reaction vesselare comprised by the total pressure with which the measuring cell isemptied or filled; in the fourth place, the dimensions of the measuringcell, capillary and pressure must be selected so that the How in thecapillary during emptying or filling the measuring cell remainslaminary; in the fifth place, the measuring result must be made visiblein one way or another, such as by means of a time recorder and/orregistration on a recorder.

What is claimed is:

1. An apparatus for measuring the viscosity of a liquid product in avessel by measuring the flow time of a predetermined amount of saidliquid product through a capillary, comprising: v

a. a measuring cell including a measuring chamber of constant volume, acapillary outflow tube in communication with the measuring chamber atthe lower end thereof, and a space above the measuring chamber,

a supply of an inert gas under a predetermined pressure, r

. a conduit system between the gas supply and the measuring cell forcirculating gas through the measuring cell, the conduit system includinga first conduit opening into the space above the measuring chamber, asecond conduit opening into the measuring chamber at the upper endthereof, and a third conduit opening adjacent to the capillary tube, v

. means in said conduit system for reversing the flow of thegas thereinbetween a liquid filling cycle, ,wherein the gas circulates through thefirst conduit, said space and out the second conduit, until the liquidfills the measuring chamber and blocks the second conduit, and a liquidemptying cycle, wherein the gas from thesecond conduit presses theliquid out of the measuring chamber through the capillary tube,

. electrical control means for actuating s id flow reversing means, and

f. a time recording means, the control means switching on the timerecording means and actuating the flow reversing means when the liquidblocks the second conduit, and switching off the time recording means inresponse to the gas pressure drop in the measuring cell at the momenttheliquid has been fully pressed out of the measuring chamber throughthecapillary tube;

2. The apparatus of claim 1, further comprising a time-delay relay inthe electrical control means for subsequently supplying the inert'gas ata lower'than said predetermined pressure to saidconduit system forfilling the measuring chamber with the liquid.

3, The apparatus of claim 1, wherein the electrical control meanscomprises a switching means for switching on the time recording means,which includes a vessel containing an electrically conductive liquid anda pair of electrodes positioned therein at different levels, the vesselbeing in communication with the conduit system. and the level of theconductive liquid in a predetermined amount of said liquid productthrough said vessel being depressed under the increased pressure in theconduitsystem when the second conduit is blocked, and the depression ofthe level of the conductive liquid causing interruption of theelectrical contact between the electrodes.

4. The apparatus of claim 1, .wherein the electrical I occurring at themoment all the liquid has been pressed out of the measuring'chamber.

5. The apparatus of claim 1, further comprising an immersion tubesurrounding the measuring cell and at least partially immersed in the.liquid in the reaction vessel, the immersion tube extending beyond thecapillary tube and having ports for circulating the liquid in thereaction vessel through the immersion tube.

6. The apparatus of claim 1, wherein the electrical control meanscomprises a switching means for switching on the time recording meanswhich consists of a pressure differential sensitive switch actuated bythe pressure rise occurring in the conduit system when the secondconduit is blocked. I

7. The apparatus ofclaim 1, comprising a pressure balanced reducingvalve for pressing'out the liquid from the measuring chamber under aconstant overpressure, and wherein the electrical control meanscomprises a switching means for switching off the time recording meanswhich consists of a pressure differential sensitive switch actuated bythe pressure drop occurring in the conduit system when the liquid has Ibeen fully pressed out of the measuring chamber.

8. The apparatus of claim 1, wherein the third conduit opens at the samelevel as the capillary tube. 1

9. The apparatus of claim I, wherein the third conoccurring in theconduit system when the liquid has been fully pressed out of themeasuring chamber.

10. An apparatus for measuring the viscosity of a liquid product in avessel by measuring the flow time of a capillary, comprising:

a. a measuring cell including a capillary outflow tube at the lower endthereof, b. a supply of an inert gas under a predetermined pressure, c.a first conduit between the gas supply and the measuring cell whichconduit has an outlet opening in the upper end of the measuring cell, d.a three-way valve in the first conduit e. a second conduit connected to,said three-way valve which second conduit opens below the liquid levelin the vessel beside the measuring cell at a level substantially abovethat of the capillary tube, f. two conductivity measuring devices atdifferent levels in the measuring cell but both below the opening of thesecond conduit, and g. a time recording means, the conductivitymeasuring devices, respectively, switching on and off the time recordingmeans when the liquid which rises in the measuring cell successivelyreaches the conductivity measuring device at the lower level and at thehigher level. 1 11. An apparatus for measuring the viscosity of a liquidproduct in a vessel by measuring the flow time of a predetermined amountof said liquid product through a capillary, comprising:

a. a measuring cell including a capillary outflow tube at the lower endthereof, b. a supply of an inert gas under a predetermined pressure, I gcja first conduit between the gas supply and the measuring cell .whichconduit has an outlet opening in the'upper end of the measuring cell, Id. a three-way valve in the first conduit,

e. a second conduit connected to said three-way valve which secondconduit opens below the liquid I ferent levels in the measuring cell butboth below the opening of the second conduit and v g, a time recordingmeans, the electrical capacity measuring devices, respectively,switching on and off the. time recording means when the liquid whichrises in the measuring cell successively reaches the electrical capacitymeasuring device at the lower level and at the higher level.

12. An apparatus for measuring the viscosity of a liquid product in avessel by measuring the flow time of a predetermined amount of saidliquid product through a capillary, comprising:

a. a measuring cell including a capillary outflow tube at the lower endthereof,

b. a supply conduit of an inert gas under a predetermined pressurehaving an outlet in the liquid in the vessel at a level substantiallybelow that of the I capillary tube, c. a first conduit connecting, via athree-way valve, a

branch of the gas supply with the upper end of the I ing device at thehigher level switching on the time recording means when the liquidrising in the measuring cell reaches said device and the conductivitymeasuring device at the lower level switching off the time recordingmeans when the liquid being pressed out of the measuring cell reachessaid cona first conduit connecting, via a three-way valve, a

branch of the gas supply with the upper end of the measuring cell,

. two electrical capacity measuring-devices at different levels in themeasuring cell andductivity measuring device.- e. a time recordingmeans, the electrical capacity 13. An apparatus for measuring theviscosity of a meashrlhg eY e at the higher h h liquid product in avessel by measuring the flow time of the reeel'dmg means When the hqulda predetermined amount of said liquid product through measuring freaches said deviee and the a capillary, comprising: electrical capacitymeasuring device at the lower a. a measuring cell including a capillaryoutflow tube levelswitchihg Off the lime recording meahs when at the l wr d th f, the liquid being pressed out of the measuring cell b; a supplyco d it f an i gas under a predetep 15 reaches said electrical capacitymeasuring device.

mined pressure havinganoutlet in the liquid in the v v v f

2. The apparatus of claim 1, further comprising a time-delay relay inthe electrical control means for subsequently supplying the inert gas ata lower than said predetermined pressure to said conduit system forfilling the measuring chamber with the liquid.
 3. The apparatus of claim1, wherein the electrical control means comprises a switching means forswitching on the time recording means, which includes a vesselcontaining an electrically conductive liquid and a pair of electrodespositioned therein at different levels, the vessel being incommunication with the conduit system and the level of the conductiveliquid in said vessel being depressed under the increased pressure inthe conduit system when the second conduit is blocked, and thedepression of the level of the conductive liquid causing interruption ofthe electrical contact between the electrodes.
 4. The apparatus of claim1, wherein the electrical control means comprises a switching means forswitching off the time recording means, which includes a vesselcontaining an electrically conductive liquid and a pair of electrodespositioned therein at different levels, the vessel being incommunication with the second conduit and the level of the conductiveliquid in said vessel being normally depressed to interrupt electricalcontact between the electrodes under the pressure of the gas supplied tothe third conduit, and the level of the conductive liquid rising toestablish electrical contact between the electrodes by a pressure dropoccurring at the moment all the liquid has been pressed out of themeasuring chamber.
 5. The apparatus of claim 1, further comprising animmersion tube surrounding the measuring cell and at least partiallyimmersed in the liquid in the reaction vessel, the immersion tubeextending beyond the capillary tube and having ports for circulating theliquid in the reaction vessel through the immersion tube.
 6. Theapparatus of claim 1, wherein the electrical control means comprises aswitching means for switching on the time recording means which consistsof a pressure differential sensitive switch actuated by the pressurerise occurring in the conduit system when the second conduit is blocked.7. The apparatus of claim 1, comprising a pressure balanced reducingvalve for pressing out the liquid from the measuring chamber under aconstant overpressure, and wherein the electrical control meanscomprises a switching means for switching off the time recording meanswhich consists of a pressure differential sensitive switch actuated bythe pressure drop occurring in the conduit system when the liquid hasbeen fully pressed out of the measuring chamber.
 8. The apparatus ofclaim 1, wherein the third conduit opens at the same level as thecapillary tube.
 9. The apparatus of claim 1, wherein the third conduitopens at a level substantially below that of the capillary tube andwherein the electrical control means comprises a switching means forswitching off the time recording means which consists of a pressuredifferential sensitive switch actuated by the pressure drop occurring inthe conduit system when the liquid has been fully pressed out of themeasuring chamber.
 10. An apparatus for meaSuring the viscosity of aliquid product in a vessel by measuring the flow time of a predeterminedamount of said liquid product through a capillary, comprising: a. ameasuring cell including a capillary outflow tube at the lower endthereof, b. a supply of an inert gas under a predetermined pressure, c.a first conduit between the gas supply and the measuring cell whichconduit has an outlet opening in the upper end of the measuring cell, d.a three-way valve in the first conduit e. a second conduit connected tosaid three-way valve which second conduit opens below the liquid levelin the vessel beside the measuring cell at a level substantially abovethat of the capillary tube, f. two conductivity measuring devices atdifferent levels in the measuring cell but both below the opening of thesecond conduit, and g. a time recording means, the conductivitymeasuring devices, respectively, switching on and off the time recordingmeans when the liquid which rises in the measuring cell successivelyreaches the conductivity measuring device at the lower level and at thehigher level.
 11. An apparatus for measuring the viscosity of a liquidproduct in a vessel by measuring the flow time of a predetermined amountof said liquid product through a capillary, comprising: a. a measuringcell including a capillary outflow tube at the lower end thereof, b. asupply of an inert gas under a predetermined pressure, c. a firstconduit between the gas supply and the measuring cell which conduit hasan outlet opening in the upper end of the measuring cell, d. a three-wayvalve in the first conduit, e. a second conduit connected to saidthree-way valve which second conduit opens below the liquid level in thevessel beside the measuring cell at a level substantially above that ofthe capillary tube, f. two electrical capacity measuring devices atdifferent levels in the measuring cell but both below the opening of thesecond conduit and g. a time recording means, the electrical capacitymeasuring devices, respectively, switching on and off the time recordingmeans when the liquid which rises in the measuring cell successivelyreaches the electrical capacity measuring device at the lower level andat the higher level.
 12. An apparatus for measuring the viscosity of aliquid product in a vessel by measuring the flow time of a predeterminedamount of said liquid product through a capillary, comprising: a. ameasuring cell including a capillary outflow tube at the lower endthereof, b. a supply conduit of an inert gas under a predeterminedpressure having an outlet in the liquid in the vessel at a levelsubstantially below that of the capillary tube, c. a first conduitconnecting, via a three-way valve, a branch of the gas supply with theupper end of the measuring cell, d. two conductivity measuring devicesat different levels in the measuring cell and e. a time recording means,the conductivity measuring device at the higher level switching on thetime recording means when the liquid rising in the measuring cellreaches said device and the conductivity measuring device at the lowerlevel switching off the time recording means when the liquid beingpressed out of the measuring cell reaches said conductivity measuringdevice.
 13. An apparatus for measuring the viscosity of a liquid productin a vessel by measuring the flow time of a predetermined amount of saidliquid product through a capillary, comprising: a. a measuring cellincluding a capillary outflow tube at the lower end thereof, b. a supplyconduit of an inert gas under a predetermined pressure having an outletin the liquid in the vessel at a level substantially below that of thecapillary tube, c. a first conduit connecting, via a three-way valve, abranch of the gas supply with the upper end of the measuring cell, d.two electrical capacity measuring devices at different levels in themeasuring cell and e. a timE recording means, the electrical capacitymeasuring device at the higher level switching on the time recordingmeans when the liquid rising in the measuring cell reaches said deviceand the electrical capacity measuring device at the lower levelswitching off the time recording means when the liquid being pressed outof the measuring cell reaches said electrical capacity measuring device.